design and simulation of a solar pv system - BRAC University ...

5.2.2 Irradiance and insolation
Insolation: Insolation is the amount of solar energy that strikes a given area over a
specific time and varies with latitude or the seasons [19].
Irradiation: Irradiance means the amount of electromagnetic energy incident on the
surface per unit time per unit area. so the total solar irradiation is defined as the amount
of radiant energy emitted by the sun over all wavelengths that falls each second on 1m 2
(11 ft 2 ) outside earth’s atmosphere [19]
Irradiance of a site is given by the following relation:
Average Insolation
Irradiance �
Average daily bright sunshine hours
, kWh / m
It is very important to know the irradiation and insolation of a site when anyone is going
to design a solar PV system for that site. Depending on the sun shine, irradiance and
insolation varies with place to place.
The irradiance of the Dhaka city can be calculated from Tables 3 and 4.
Table 4. Monthly global solar insolation in Dhaka city
Month Solar Insolation
kWh/m 2
January 5.47
February 5.91
March 6.00
April 5.85
May 5.23
June 4.55
July 4.18
August 4.60
September 4.94
October 5.44
November 5.34
December 5.38
Average 5.24
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